Baggs notes that the trip was "believed to be a precaution," and Williams condition currently isn't known.

"I think he's feeling much better right now than he did when he left, but we're taking this one step at a time, and hopefully it's not something serious," Angels manager Mike Scioscia said. "Unfortunately, his outing wasn't what he anticipated or what we needed, but now, we're dealing with a bigger issue, and hopefully he'll be fine."

Williams is a former first-round pick by the Giants, who took him with the 39th-overall selection in the 1999 draft out of high school.

He went 17-14 with the Giants in two-and-a-half years in San Francisco, posting a 3.93 ERA over 277 innings while striking out 179.